WO2018037810A1 - Machine component and extruded material - Google Patents

Abstract

A machine component characterized by comprising an aluminium alloy containing 8.0-14.0 mass% of Zn, 2.0-4.0 mass% of Mg, 0.5-2.0 mass% of Cu, 0.2-1.5 mass% of Mn and 0.05-0.3 mass% of Zr, with the remainder being Al and unavoidable impurities, wherein the mean particle diameter of the fine particles within the crystal grains measured by small-angle X-ray scattering is 2-7 nm, the normalized dispersion of the particle size distribution is no more than 45%, the tensile strength is 800 MPa or higher, and the total elongation is 5% or more.

Description

Machine parts and extruded materials

The present disclosure relates to a machine part made of an aluminum alloy and an extruded material. More specifically, the present invention relates to a machine part and an extruded material made of a 7000 series aluminum alloy.

Conventionally, as materials for various machine parts such as bolts and nuts, and springs (springs), Al—Zn—Mg—Cu-based aluminum alloys having excellent strength, corrosion resistance and light weight (hereinafter, Extruded material made of 7000 series aluminum alloy is sometimes used.

Extruded materials made of a 7000 series aluminum alloy have high strength, and various types of materials having a tensile strength of 700 MPa or higher by T6 refining after extrusion have been proposed.

For example, Patent Document 1 discloses that a 7000 series aluminum alloy wire rod extruded material having a Zn content exceeding 8 mass% can be easily imparted with a strength exceeding a tensile strength of 720 MPa by aging treatment. However, in the extruded material according to the same document, a coarse recrystallized grain layer is formed, which causes cracking when the extruded material is subjected to plastic processing (forming processing) such as forging or rolling into a large-diameter bolt. . For this reason, it is essential to remove the coarse recrystallized grain layer on the surface of the extruded material (surface layer portion) before plastic working.

In contrast, various attempts to suppress such a recrystallized grain layer have been proposed. For example, in Patent Document 2, the extrusion temperature is made at a relatively low temperature of 480 to 500 ° C., the inside of the extruded 7000 series aluminum alloy has a fibrous structure, the thickness of the recrystallized layer of the surface layer is 10% or less, It is disclosed that the recrystallized grain size is controlled to 150 μm or less.
However, even if the extrusion temperature is a relatively low temperature of 480 to 500 ° C. as in Patent Document 2, the 7000 series aluminum alloy is also recrystallized in the extrusion in this temperature range. In addition, recrystallization inside is inevitable, and there is a possibility that a strength of 700 MPa or more cannot be obtained with good reproducibility and tensile strength.

On the other hand, Patent Document 3 discloses manufacturing a 7000 series aluminum alloy extruded material by hot isostatic pressing. In the extruded material, the average crystal grain size of the recrystallized grains in the surface layer portion of the extruded material is 100 μm or less as a cross-sectional structure parallel to the extrusion direction passing through the axial center portion of the extruded material in the extruded state. In addition, the average intercept length in the radial direction of the crystal grains in the central portion of the extruded material axis is 35 μm or less, and the average area ratio of the <111> orientation crystal grains in the extrusion direction is 0.5 or more and 1.0 or less. Thus, it is disclosed that the ratio <001> / <111> between the average area ratio of <001> oriented crystal grains and the average area ratio of <111> oriented crystal grains is 0.25 or less.

In Patent Document 3, as a result of the structure of the extruded material that has not been subjected to any heat treatment or processing other than cooling from the extrusion temperature after completion of the hot extrusion, and remains extruded (extruded), the surface layer In addition to the portion, recrystallization (recrystallization) inside the extruded material is also suppressed. Thus, it is disclosed that a fine extruded structure (fibrous structure) is obtained and a high strength of 700 MPa or more is obtained as a tensile strength after artificial aging treatment.
However, even in Patent Document 3, as shown in Table 3 of the examples, the tensile strength after the artificial aging treatment obtained is 700 MPa or more, but it is only less than about 800 MPa.

Patent Document 4 discloses a 7000 series aluminum alloy rolled plate for automobile structural members such as frames and pillars, not extruded materials. In this document, in order to increase the strength, as the crystal orientation structure of the rolled plate, the average crystal grain size is 15 μm or less, and the average proportion of the low-angle grain boundaries with an inclination of 5 to 15 ° is 15% or more. It has also been proposed that the average proportion of grain boundaries with a large tilt angle exceeding 15 ° is 15 to 50%.
However, in the case of Patent Document 4, the tensile strength after the obtained artificial aging treatment is less than 500 MPa as shown in Table 2 of Examples, and such a metallurgical method using a rolled sheet is a plastic working method and manufacturing. Whether or not the method is really effective for increasing the strength of 800 MPa or more of different extruded materials and machine parts can only be confirmed by actually testing.

JP 2010-236665 A JP-A-8-170139 JP 2014-125676 A JP 2014-62287 A

Thus, although the conventional 7000 series aluminum alloy extruded material can achieve a certain level of strength, it is difficult to stably obtain sufficient strength as a material for mechanical parts such as bolts and springs that require high strength. There was a case.

An embodiment of the present invention has been made to solve such a problem, and the purpose thereof is a 7000 series in which the tensile strength after artificial aging treatment is 800 MPa or more and the total elongation is 5% or more. It is to provide a mechanical part made of an aluminum alloy, and to provide a 7000 series aluminum alloy extruded material capable of producing a mechanical part having such excellent mechanical properties.

In aspect 1 of the present invention, Zn: 8.0 to 14.0 mass%, Mg: 2.0 to 4.0 mass%, Cu: 0.5 to 2.0 mass%, Mn: 0.2 to 1 .5% by mass, Zr: 0.05 to 0.3% by mass, and the balance is a mechanical part made of an aluminum alloy containing Al and unavoidable impurities, with crystal grains measured by X-ray small angle scattering. The average particle diameter of the fine particles is 2 nm or more and 7 nm or less, the normalized dispersion of the particle size distribution is 45% or less, the tensile strength is 800 MPa or more, and the total elongation is 5% or more. It is a part.

Aspect 2 of the present invention is the mechanical component according to aspect 1, further containing one or two of Cr: 0.05 to 0.3% by mass and Sc: 0.05 to 0.3% by mass. .

Aspect 3 of the present invention is the mechanical part according to Aspect 1 or 2, further comprising one or two of Ag: 0.05 to 0.5 mass% and Sn: 0.01 to 0.2 mass%. It is.

In aspect 4 of the present invention, Zn: 8.0 to 14.0% by mass, Mg: 2.0 to 4.0% by mass, Cu: 0.5 to 2.0% by mass, Mn: 0.2 to 1 .5 mass%, Zr: 0.05 to 0.3 mass%, and the balance is an extrusion material for machine parts made of an aluminum alloy containing Al and unavoidable impurities. Is a wire rod extruded material having a circular diameter of 25 mm, and drawn to a wire rod material having a circular area of 10 mmφ with an area reduction rate of 84%, and this wire rod material is held at a temperature of 480 ° C. for 5 hours. After solution treatment, quenching treatment was performed at an average cooling rate of up to 50 ° C. at 200 ° C./second, and then artificial aging treatment was performed at 120 ° C. for 72 hours. The average particle diameter of the fine particles is 2 nm or more and 7 nm or less. Dispersion is 45% or less, a tensile strength of at least 800 MPa, an extruded material, wherein the total elongation is 5% or more.

Aspect 5 of the present invention is the extruded material according to aspect 4, further containing one or two of Cr: 0.05 to 0.3% by mass and Sc: 0.05 to 0.3% by mass. .

Aspect 6 of the present invention is the extruded material according to aspect 4 or 5, further comprising one or two of Ag: 0.05 to 0.5% by mass and Sn: 0.01 to 0.2% by mass. It is.

According to an embodiment of the present invention, there is provided a mechanical component made of a 7000 series aluminum alloy having a tensile strength after artificial aging treatment of 800 MPa or more and a total elongation of 5% or more, and such an excellent machine. It is possible to provide a 7000 series aluminum alloy extruded material capable of producing mechanical parts having specific characteristics.

The inventors of the present invention can manufacture a mechanical part made of a 7000 series aluminum alloy having sufficiently excellent mechanical characteristics as a mechanical part such as a bolt and a spring, and 7000 capable of manufacturing a mechanical part having such excellent mechanical characteristics. In order to realize an aluminum alloy extruded material, it was examined from various angles.
As a result of intensive studies, the present inventors have determined that the precipitates present at the grain boundaries by controlling the average particle diameter of the fine particles in the grains measured by X-ray small angle scattering and the normalized dispersion of the grain size distribution. From a 7000 series aluminum alloy having a tensile strength after artificial aging treatment of 800 MPa or more and a total elongation of 5% or more. It has been found that mechanical parts can be provided.

Below, the detail of the machine component and extrusion material which concern on embodiment of this invention is shown.
It should be noted that the aluminum alloy composition and structure described below are related to the common significance of the mechanical component and the extruded material according to the embodiment of the present invention.
“Machine parts” as used herein refers to various parts such as bolt and nut thread parts, gears (shafts), bearings (bearings), and springs (springs) made of extruded material. It is a machine element as a functional unit of the smallest unit commonly used in various machines.
As used herein, “after artificial aging treatment” means “after solution treatment and quenching treatment and artificial aging treatment”.

1. Organization The mechanical component according to the embodiment of the present invention can be manufactured using the extruded material according to the embodiment of the present invention as a raw material as described later. Therefore, the mechanical component according to the embodiment of the present invention has fine nano-sized precipitates (in the present specification, sometimes referred to as fine particles), similar to the extruded material according to the embodiment of the present invention. Many exist in the crystal grains and achieve high strength.

This fine particle is an intermetallic compound of Mg and Zn (composition is MgZn ₂ or the like) formed in the crystal grain, and further contains contained elements such as Cu and Zr according to other alloy compositions. It is a finely dispersed phase. In addition, the size of the fine particles referred to in the embodiment of the present invention means an equivalent circle diameter of fine particles that are indefinite.

1-1. Mechanical part The mechanical part according to an embodiment of the present invention is an extruded fine structure after artificial aging treatment, an average particle diameter of fine particles in crystal grains measured by X-ray small angle scattering, a normalized dispersion of particle size distribution, By controlling the ratio, it is possible to achieve both excellent strength and elongation.

Specifically, the structure after artificial aging treatment of a machine part manufactured by cold working a 7000 series aluminum alloy extrudate, which is a raw material, is a fine particle size measured in a crystal grain by the X-ray small angle scattering method. The average particle diameter of the distribution is controlled to be 2 nm or more and 7 nm or less, and the normalized dispersion of the particle size distribution is controlled to be 45% or less.

Thus, by controlling the average particle diameter of the fine particles measured by the X-ray small angle scattering method and the normalized dispersion indicating the spread of the particle size distribution, the tensile strength after aging treatment is 800 MPa or more. High strength can be achieved. At the same time, it is possible to suppress the precipitation of precipitates existing at the grain boundaries and coarse precipitates existing within the crystal grains, thereby achieving excellent strength and excellent elongation.

(1) Average particle diameter: 2 nm or more and 7 nm or less If the average particle diameter of the fine particles is too small, since the action as an obstacle to dislocation during deformation is small, high strength cannot be achieved. Therefore, the average particle diameter is 2 nm or more, preferably 3 nm or more.
On the other hand, if the average particle diameter of the fine particles is too large, the distance between the particles becomes large and the action as an obstacle to dislocation becomes small. Furthermore, the production | generation of the precipitate which exists in a crystal grain boundary, and the coarse precipitate which exists in a crystal grain increases, and there exists a possibility that elongation may fall. Therefore, the average particle diameter is 7 nm or less, preferably 6 nm or less.

(2) Normalized dispersion of particle size distribution Normalized dispersion of particle size distribution is an index indicating the spread of particle distribution. That is, when the normalized dispersion is large, it means that the particles are widely distributed from small particles to large particles. Conversely, when the normalized dispersion is small, it means that the difference between large particles and small particles is relatively small.

If the normalized dispersion of the particle size distribution is too large, the action of the particles as an obstacle to dislocation during deformation becomes non-uniform and high strength cannot be achieved. Therefore, the normalized dispersion of the particle size distribution is 45% or less, preferably 40% or less.
Note that the normalized dispersion of the particle size distribution has a production limit even by controlling the composition and heat treatment, and the lower limit can be reduced only to about 10%.

In the embodiment of the present invention, the fine particles having a particle diameter of 2 nm or more and 7 nm or less, the average particle diameter of the particle size distribution, and the normalized dispersion of the particle size distribution are too fine for the optical microscope used in the prior art. Therefore, it cannot be observed and measured, and can be evaluated by the prescribed X-ray small angle scattering method.

1-2. Aluminum Alloy Extruded Material The mechanical component according to the embodiment of the present invention described above can achieve both excellent strength and elongation by manufacturing using the aluminum alloy extruded material according to the embodiment of the present invention as a material. . Specifically, an embodiment of the present invention that is excellent in strength and elongation by performing solution treatment, quenching treatment and artificial aging treatment on the aluminum alloy extruded material according to the embodiment of the present invention under the conditions described later. Can be obtained.

Such characteristics of the aluminum alloy extruded material according to the embodiment of the present invention are particularly remarkable by processing the alloy extruded material to simulate a mechanical part under a predetermined condition and performing measurement on the workpiece. Can be expressed.
Therefore, in the embodiment of the present invention, an aluminum alloy is processed by imitating a machine part under a predetermined condition with respect to an alloy extruded material, and evaluating the structure and mechanical characteristics of the non-processed part. Extruded material is specified.
Below, the concrete process conditions for evaluating an aluminum alloy extruded material concrete are described.

The aluminum alloy extruded material according to the embodiment of the present invention is processed into a wire rod extruded material having a circular cross section, and then drawn into a wire rod material, and the wire rod material is subjected to solution treatment and quenching treatment. And after performing an artificial aging treatment, the characteristic can be evaluated by measuring the average dispersion | distribution of the average particle diameter and particle size distribution of a fine particle using X-ray small angle scattering.

Specifically, the alloy extruded material according to the embodiment of the present invention is a wire rod extruded material having a circular cross-sectional shape and a diameter of 25 mm, and is drawn and drawn at a reduction rate of 84% to obtain a circular shape having a cross-section of 10 mmφ. To be a wire rod material. Then, the wire rod material is subjected to a solution treatment that is held at a temperature of 480 ° C. for 5 hours, and then subjected to a quenching treatment at an average cooling rate up to 50 ° C. of 200 ° C./second, and then at 120 ° C. for 72 hours Apply artificial aging treatment. Thus, by measuring a structure | tissue by the X-ray small angle scattering method mentioned later with respect to the obtained non-working object, and measuring a mechanical characteristic by a tensile test, the alloy extrusion material which concerns on embodiment of this invention Can be evaluated. The “circular cross section” includes a perfect circle, an ellipse, and a substantially circular shape.

When the alloy extruded material according to the embodiment of the present invention is processed as described above and then the structure and mechanical properties are evaluated, the average particle diameter of the fine particles in the crystal grains measured by X-ray small angle scattering is 2 nm. As mentioned above, it is 7 nm or less, the normalized dispersion of the particle size distribution is 45% or less, the tensile strength is 800 MPa or more, and the total elongation is 5% or more. Since the alloy extruded material according to the embodiment of the present invention has such characteristics, a mechanical component excellent in both strength and elongation can be obtained by producing a mechanical component using the alloy extruded material as a raw material. Can do.

In the aluminum alloy extruded material according to the embodiment of the present invention, the average particle diameter of the fine particles obtained by processing and measuring in this way and the normalized dispersion of the particle size distribution are strictly controlled within a predetermined range. When a machine part is manufactured using the alloy extruded material, a machine part having excellent strength and elongation can be provided.

2. Evaluation of tissue (1) Small-angle scattering method using X-rays The small-angle scattering method itself using X-rays has long been known as a representative method for examining structural information on the order of nanometers. When a substance is irradiated with X-rays, the incident X-rays reflect information on the electron density distribution inside the substance, and scattered X-rays are generated around the incident X-rays. For example, if a particle or an electron density non-uniform region exists in a substance, X-rays interfere with each other regardless of crystal or amorphous, and scattering due to density fluctuation occurs. If this is a metal such as an aluminum alloy, if fine particles of nanometer order exist in the aluminum alloy structure, scattering derived from the particles is observed. In the region where the scattered X-rays are generated, the measurement angle 2θ is about 0.1 to 10 degrees or less in the case of X-rays having a wavelength of 1.54 mm using a Cu target. In the X-ray small angle scattering method, by analyzing the scattered X-rays, it is possible to obtain information on the shape, size and distribution of fine particles on the order of nanometers.

For example, in Japanese Patent Application Laid-Open No. 2011-38136, etc., the average particle diameter of the particle size distribution of fine particles related to the generation of stretcher strain marks during the press forming of a 5000 series Al—Mg series aluminum alloy plate, and the grain size distribution It is used to measure the number density of the peak size.

In order to measure the average particle diameter of the particle size distribution of the fine particles of the aluminum alloy structure and the number density of the peak size of this particle size distribution, first, the X-ray of the aluminum alloy plate measured by the X-ray small angle scattering method was used. Determine the scattering intensity profile. The X-ray scattering intensity profile is obtained, for example, as the X-ray scattering intensity (scattering X-ray scattering intensity) on the vertical axis and the wave vector q (nm ⁻¹ ) depending on the measurement angle 2θ and wavelength λ on the horizontal axis. .

In the embodiment of the present invention, the average particle diameter of fine particles that are 2 nm or more and 7 nm or less, and the normalized dispersion indicating the spread of the particle size distribution can be obtained from the X-ray scattering intensity profile. That is, by performing fitting by the nonlinear least square method so that the measured X-ray scattering intensity is close to the X-ray scattering intensity calculated from the theoretical expression represented by the function of the particle diameter and size distribution, the particle diameter and A normalized dispersion value can be obtained.

Incidentally, as an analysis method (analysis software) for analyzing the X-ray scattering intensity profile and obtaining the particle size distribution of the fine precipitates, for example, a well-known analysis method by Schmidt et al. May be used (IS FEDOROVAAND). P. Schmidt: J. Appl. Cryst. 11, 405, 1978).

(2) X-ray small-angle scattering measurement apparatus As such an X-ray small-angle scattering measurement apparatus, a representative small-angle scattering apparatus is disclosed in, for example, Japanese Patent Application Laid-Open No. 9-119906. Then, X-rays are irradiated at a minute angle (small angle), and X-rays scattered from the sample are measured using a detector such as a two-dimensional multi-wire type.

The region where the scattered X-rays are generated is a small angle of about 0.1 to 10 degrees or less in the case of X-rays having a wavelength of 1.54 mm. By analyzing this scattered X-ray as described above, it is possible to obtain information on the shape, size, and distribution of the particles, such as the particle size distribution.

3. Chemical composition:
Next, the composition of the machine part and the extruded material according to the embodiment of the present invention will be described. The machine part and the extruded material according to the embodiment of the present invention are made of a 7000 series aluminum alloy, and the component composition only needs to have a normal chemical composition as a 7000 series aluminum alloy.

(1) Zn: 8.0 to 14.0% by mass
Zn, together with Mg, is an element that improves the strength by forming an aging precipitate that is an intermetallic compound of Mg and Zn during an artificial aging treatment described later.
If the Zn content is less than 8.0% by mass, the strength as a machine part is insufficient. Therefore, Zn content is 8.0 mass% or more, Preferably it is 9.0 mass% or more.
On the other hand, if the Zn content exceeds 14.0% by mass, ingot cracking is likely to occur during casting of the billet for the extruded material, and ingot making becomes difficult. Therefore, Zn content is 14.0 mass% or less, Preferably it is 13.0 mass% or less.
In addition, when Zn content is high, SCC sensitivity becomes sharp, but in order to suppress it, it is desirable to add Cu or Ag described later.

(2) Mg: 2.0 to 4.0% by mass
Mg, together with Zn, is an element that improves the strength and elongation as a mechanical component by forming an aging precipitate, which is an intermetallic compound of Mg and Zn, defined in the embodiment of the present invention during the artificial aging treatment described later. is there.
If the Mg content is less than 2.0% by mass, the strength is insufficient. Therefore, the Mg content is 2.0% by mass or more, preferably 2.5% by mass or more.
On the other hand, if the Mg content exceeds 4.0% by mass, the extrudability at a low temperature in the non-recrystallization temperature range (temperature range below the recrystallization temperature) of the cast billet for the extruded material is lowered, and the SCC sensitivity is reduced. Become stronger. Therefore, Mg content is 4.0 mass% or less, Preferably it is 3.5 mass% or less.

(3) Cu: 0.5 to 2.0 mass%
Cu has the effect of improving the SCC resistance as a machine part.
When the Cu content is less than 0.5% by mass, the effect of improving the SCC resistance is small. Therefore, the Cu content is 0.5% by mass or more, and preferably 0.7% by mass or more.
On the other hand, if the Cu content exceeds 2.0% by mass, cracks are likely to occur during casting of the cast billet for the extruded material, and the extrudability of the cast billet is lowered. Therefore, Cu content is 2.0 mass% or less, Preferably it is 1.8 mass% or less.

(4) Mn: 0.2 to 1.5% by mass
In addition to refining crystal grains, Mn contributes to improving the strength of mechanical parts by forming dispersed particles.
When the Mn content is less than 0.2% by mass, the content is insufficient and the strength is lowered. Therefore, the Mn content is 0.2% by mass or more, preferably 0.3% by mass or more.
On the other hand, when the Mn content exceeds 1.5% by mass, a coarse crystallized product is formed, resulting in a decrease in elongation. Therefore, the Mn content is 1.5% by mass or less, preferably 1.2% by mass or less.

(5) Zr: 0.05 to 0.3% by mass
Zr forms fine precipitates, suppresses recrystallization, and contributes to improving the strength of machine parts.
When the content of Zr is less than 0.05% by mass, the content is insufficient and the strength is lowered. Therefore, the Zr content is 0.05% by mass or more, preferably 0.1% by mass or more.
On the other hand, when the content of Zr exceeds the upper limit, a coarse crystallized product is formed, so that the elongation decreases. Therefore, the Zr content is 0.3% by mass or less, preferably 0.25% by mass or less.

(6) Balance In one preferred embodiment, the balance is Al and inevitable impurities. As unavoidable impurities, it is assumed that trace elements such as Fe, Si, Ti and B brought in depending on the conditions of raw materials, materials, manufacturing facilities, and the like are mixed. However, the inclusion of each of these inevitable impurities is allowed within the range specified by JIS standards for 7000 series alloys. For example, Fe and Si are each in the range of 0.5% by mass or less (including 0% by mass), Ti is in the range of 0.1% by mass or less (including 0% by mass), and B is 0.1% by mass. Each may be contained within the following range (including 0% by mass).

The mechanical component and the extruded material according to the embodiment of the present invention are not limited to the above-described composition. As long as the characteristics of the machine part and the extruded material according to the embodiment of the present invention can be maintained, other elements may be further included as necessary. Other elements that can be selectively contained as described above are exemplified below.

(7) One or two of Cr: 0.05 to 0.3% by mass and Sc: 0.05 to 0.3% by mass Cr and Sc, like Zr, form fine precipitates, It also suppresses recrystallization and contributes to improving the strength of machine parts.
When either one or two of these are selectively contained, if the Cr and Sc contents are both less than 0.05, the strength improvement effect may not be obtained. Therefore, the Cr content is preferably 0.05% by mass or more, and more preferably 0.1% by mass or more. For the same reason, the Sc content is preferably 0.05% by mass or more, and more preferably 0.1% by mass or more.

On the other hand, when the contents of Cr and Sc each exceed 0.3% by mass, a coarse crystallized product is formed, which may reduce the elongation. Therefore, the Cr content is preferably 0.3% by mass or less, and more preferably 0.25% by mass or less. For the same reason, the Sc content is preferably 0.3% by mass or less, and more preferably 0.25% by mass or less.

(8) One or two of Ag: 0.05 to 0.5 mass% and Sn: 0.01 to 0.2 mass% Ag and Sn are non-precipitated in the vicinity of the grain boundary in the artificial aging treatment Suppresses the formation of bands and contributes to improving the strength of machine parts.
When it is selectively contained, if the Ag content is less than 0.05% by mass and / or the Sn content is less than 0.01% by mass, the effect of miniaturization may be small. . Therefore, the Ag content is preferably 0.05% by mass or more, and more preferably 0.1% by mass or more. For the same reason, the Sn content is preferably 0.01% by mass or more, and more preferably 0.03% by mass or more.

On the other hand, when the Ag content exceeds 0.5% by mass and / or when the Sn content exceeds 0.2% by mass, a coarse primary crystal compound is produced during the casting of the cast billet for the extruded material. It can form and cause seizure during extrusion and / or reduced elongation of the machine part as a product. Therefore, the Ag content is preferably 0.5% by mass or less, and more preferably 0.4% by mass or less. For the same reason, the Sn content is preferably 0.2% by mass or less, and more preferably 0.15% by mass or less.

4). Manufacturing Method The manufacturing method of the extruded material and the machine part according to the embodiment of the present invention will be described.

4-1. Extruded Material Manufacturing Method First, an extruded material (extruded profile) manufacturing method will be described below in the order of steps.

(1) Melting and casting In the melting and casting process, an aluminum alloy melt adjusted within the above-mentioned 7000 series component composition range is appropriately selected by a normal melting casting method such as a semi-continuous casting method (DC casting method). Cast into billets.

(2) Homogenization heat treatment Prior to the hot extrusion described later, the obtained aluminum alloy billet (ingot) is subjected to homogenization heat treatment (uniform heat treatment) to homogenize the structure (that is, crystal grains in the ingot structure). In order to eliminate segregation in the inside). By the homogenization heat treatment, the Zr-based compound and the compound composed of Mn, Cr and Sc are finely dispersed, and the crystal grain structure after extrusion and solution treatment is refined.

If the soaking temperature is less than 400 ° C., a sufficient effect of miniaturization cannot be obtained. Therefore, the soaking temperature is 400 ° C. or higher, preferably 410 ° C. or higher.
On the other hand, when the soaking temperature exceeds 450 ° C., these compounds are coarsened, so the effect of miniaturization is lowered. Therefore, the soaking temperature is 450 ° C. or lower, preferably 440 ° C. or lower.
The holding time during soaking is preferably about 1 to 8 hours.

(3) Hot extrusion By hot extrusion, an extruded material shape close to this final shape corresponding to the final machine part shape is obtained. By hot extrusion, not only the surface layer portion of the extruded material but also recrystallization inside the extruded material can be suppressed, and a fine extruded structure can be obtained.
When the extrusion start temperature exceeds 400 ° C., the temperature at the time of extrusion rises and recrystallization tends to occur at a high temperature, and not only a coarse recrystallized structure is formed in the surface layer portion and the inside of the extruded material, but also coarse particles Precipitates, resulting in a decrease in strength. Therefore, extrusion start temperature is 400 degrees C or less, Preferably it is 380 degrees C or less.
On the other hand, the lower the extrusion start temperature, the better. However, if it is too low, the deformation resistance increases and the extrusion becomes difficult. Therefore, the extrusion start temperature is preferably 300 ° C. or higher, more preferably 320 ° C. or higher.

The extrusion speed is preferably 10 m / min or less in order to suppress processing heat generated during extrusion and suppress the recrystallization during extrusion. More preferably, it is 7 m / min or less.

By setting the average cooling rate from after hot extrusion to 50 ° C. within a predetermined range, precipitation of particles containing Zn and Mg generated during this cooling can be suppressed. When the cooling rate in the said temperature range is less than 2 degree-C / sec, the amount of solid solution Zn and solid solution Mg reduces, the diameter of the fine particle after artificial aging treatment exceeds 7 nm, and intensity | strength falls. Therefore, the average cooling rate up to 50 ° C. is 2 ° C./second or more, and preferably 4 ° C./second or more.

Such an average cooling rate of 2 ° C./second or more can be achieved by providing a cooling means. Examples of the cooling means include air cooling using a fan and water cooling.

As the extrusion method, direct extrusion or indirect extrusion may be used, but there are cases where many seizures occur under the preferable extrusion conditions in the non-recrystallized region. Therefore, when extrusion is difficult, it is preferable to carry out by hydrostatic extrusion.

Direct extrusion and indirect extrusion are more efficient than hydrostatic extrusion, but the recrystallized grain layer on the surface of the extruded material (surface portion) is relatively fine, fibrous crystals extending in the extrusion direction. There is a problem that it becomes easy to become a grainy coarse crystal grain as compared with a grain (extrusion process) structure. Further, as in the embodiment of the present invention, when extruding a 7000 series aluminum alloy having a Zn content exceeding 8% by mass, in the case of direct extrusion or indirect extrusion, extrusion below the recrystallization temperature range Processing is quite difficult.

This is because, even if the billet, which is an extrusion material, has a heating temperature lower than the recrystallization temperature range, in the case of direct extrusion or indirect extrusion, the billet is extruded in contact with the container wall surface and the die due to the structure of the extruder. Frictional heat is generated. As a result, the temperature during extrusion becomes the recrystallization temperature range. For this reason, a coarse recrystallized (grain) layer which causes a problem in Patent Document 1 is easily formed on the surface layer portion of the extruded material.

On the other hand, in hot isostatic pressing, a lubricant is put between the container and the billet, and a state in which the billet for extrusion floats in this lubricant is pushed out by a stem (with a dummy block). . Thus, the billet is not in direct contact with the container and die due to the action of this lubricant, unlike direct and indirect extrusion. That is, the billet is in direct contact only while it passes through about 5 mm of the die thickness. As a result, friction and heat of friction are also reduced, and the metal flow becomes nearly uniform. As a result, even a billet of a 7000 series aluminum alloy as in the embodiment of the present invention having a high Zn content can be extruded even at a low temperature below the recrystallization temperature, and the surface layer portion and the inside of the extruded material It becomes possible to suppress (miniaturize) the recrystallized grain layer.

For this reason, the extruded material by hot isostatic pressing includes the recrystallized grain layer, or even if there is a recrystallized grain layer, the structure from the surface layer to the inside can be made uniform. As a result, the drawability, drawability, workability, and formability of the wire rod or wire rod product are significantly improved. In addition, if the recrystallized grain layer is suppressed as in the embodiment of the present invention, the basic characteristics such as sag resistance required for wire rod products such as aluminum alloy bolts by being a fine extruded structure. Can also be guaranteed.

4-2. Manufacturing method of machine part The extruded material after hot extrusion obtained as described above is further cold-worked into the product shape of the machine part for each application.

The general processing process for machine parts such as bolts is to draw the extruded material to reduce the diameter after annealing, wash it, anneal it, and then roll or forge it into the product shape of the machine part. Good. And after completion of such product processing, solution treatment and quenching treatment are performed, and further artificial aging treatment is performed to improve the strength.

It should be noted that the annealing treatment described above is optional, and the annealing treatment may be performed during drawing or rolling. In addition, the cold working such as drawing or rolling is, of course, specific applications such as bolt and nut thread parts, gears (gears), shafts (shafts), bearings (bearings), and springs (springs). Depending on the shape, the conditions are changed.

(1) Solution treatment The solution treatment of mechanical parts may be a general heating and cooling method, and is not particularly limited. However, if the holding temperature is less than 450 ° C. or the holding time is less than 0.5 hours, the solid solution of Mg and Zn becomes insufficient and the strength may be insufficient. On the other hand, if the holding temperature exceeds 505 ° C. and the holding time exceeds 10 hours, the strength may be insufficient.
Therefore, the solution treatment is preferably held at a solution treatment temperature of 450 to 550 ° C. for 0.5 to 10 hours.

(2) Quenching treatment As a quenching treatment after the solution treatment, the cooling (temperature decrease) rate from the solution treatment temperature to 50 ° C is desirably 50 ° C / second or more on average. If the average cooling rate is too low at less than 50 ° C./second, coarse recrystallization may occur and the strength may be insufficient. In addition, coarse grain boundary precipitates that lower the strength and / or elongation are formed, and the strength may be insufficient. The upper limit of the average cooling rate is about 500 ° C./second from the limit of the equipment capacity. The cooling rate from 50 ° C. to room temperature is not particularly limited, and may be rapidly cooled as it is, or may be cooled by stopping the rapid cooling.

(3) Artificial aging treatment By performing artificial aging treatment on the machine part after solution treatment, the machine part according to the embodiment of the present invention is obtained.
When the artificial aging treatment temperature is less than 100 ° C., the amount of fine particles formed is insufficient and the strength is lowered. Therefore, the artificial aging treatment temperature is 100 ° C. or higher, preferably 120 ° C. or higher.
On the other hand, when the artificial aging treatment temperature exceeds 200 ° C., fine particles are coarsened, the particle size distribution is widened, and the strength is lowered. Therefore, the artificial aging treatment temperature is 200 ° C. or lower, preferably 180 ° C. or lower.

Moreover, when the artificial aging treatment time is less than 2 hours, the amount of fine particles formed is insufficient and the strength is lowered. Therefore, the artificial aging treatment time is 2 hours or more, preferably 4 hours or more.
On the other hand, when the artificial aging treatment time exceeds 120 hours, the fine particles become coarse and the strength decreases. Therefore, the artificial aging time is 120 hours or less, preferably 110 hours or less.

A person skilled in the art who is in contact with the above-described method for manufacturing a mechanical part and an extruded material according to the embodiment of the present invention will perform a mechanical part according to the embodiment of the present invention by a manufacturing method different from the manufacturing method described above by trial and error. And may be able to obtain extrudates.

Hereinafter, embodiments of the present invention will be described more specifically with reference to examples. The present invention is not limited by the following examples, and can be implemented with modifications within a range that can be adapted to the above-described gist, which are all included in the technical scope of the present invention. Is done.

1. Sample preparation After casting a 7000 series aluminum alloy ingot having the composition shown in Table 1, it was subjected to a homogenization treatment at a homogenization treatment temperature shown in Table 1 for a holding time of 4 hours, followed by hot isostatic pressing. A wire rod extrudate having a circular cross section and a diameter of 25 mm was produced.
As for the extrusion conditions of the wire rod extrusion material, hot isostatic extrusion was performed at the start temperature shown in Table 1 in common with each example. After hot extrusion, it was cooled to 50 ° C. or less at the average cooling rate shown in Table 1. In the cooling to 50 ° C. after the extrusion, the comparative example No. For the samples other than 8, the cooling rate was controlled by air cooling using a fan.

In common with each example, the wire rod extruded material is subjected to a drawing process with a reduction in area of 84% to simulate a machine part application to obtain a wire rod material having a circular cross section of 10 mmφ. The bar was subjected to a solution treatment at 480 ° C. for 5 hours, then water-cooled at an average cooling rate of up to 50 ° C. at 200 ° C./second, and subjected to artificial aging treatment under the conditions shown in Table 1.

Furthermore, a test piece was collected from a wire rod material simulating the mechanical part after the artificial aging treatment, and the average dispersion of the average particle diameter and the particle size distribution of fine particles in the crystal grains of the test piece structure was measured. In addition, the mechanical properties of the material after the artificial aging treatment were measured. These results are also shown in Table 1.
In Table 1, underlined numerical values indicate that they are out of the scope of the embodiment of the present invention.

The test piece collected from the wire rod material after the artificial aging treatment is a round bar smooth tensile test piece (3 mmφ × 12 mmGL), and an intermediate (middle) position (1 / D of the diameter D) between the surface of the test piece and the axis center. A surface (cross section) parallel to the extrusion direction at 4 positions) was collected so as to be an observation surface.

2. Organizational evaluation:
(X-ray small angle scattering measurement)
The X-ray small angle scattering measurement is common to each example, using a horizontal X-ray diffractometer SmartLab manufactured by Rigaku Co., Ltd., and measuring with X-rays having a wavelength of 1.54 mm. The intensity profile was measured. The test apparatus enters X-rays perpendicularly to the surface of the test piece, and emits X-rays scattered backward from the test piece at a minute angle (small angle) of 0.1 to 10 degrees with respect to the incident X-ray. It is measured using a detector. The measurement sample was sliced to about 80 μm and measured.

The X-ray scattering intensity profile is a particle size / hole analysis software manufactured by Rigaku Corporation, NANO-Solver [Ver. 3.5], the average particle diameter and the normalized dispersion are reduced by fitting by the nonlinear least square method so that the measured X-ray scattering intensity and the X-ray scattering intensity calculated by the analysis software are close to each other. Asked.

The average particle diameter was obtained by calculating the scattering intensity using a theoretical formula and fitting it with an experimental value, assuming that the particles are perfectly spherical. The normalized dispersion was used to enable comparison of particle distribution spreads regardless of particle diameter.

The normalized dispersion formula is shown below.

Here, σ is the normalized dispersion, n is the number of particles, x is the particle diameter, and <x> is the arithmetic mean of the particle diameter.

3. Measurement of mechanical properties As for the mechanical properties of the round bar smooth tensile test piece, a tensile test was performed until breakage at room temperature at a crosshead speed of 12 mm / min. The tensile strength (MPa) was measured from the stress-strain rate. The total elongation (%) was calculated from the spacing between the marking lines before and after the tensile test during the tensile test (10 mm before the tensile test). In addition, these measured values were made into the average value of the said 5 test pieces in each example.

4). Summary Invention No. 1 in Table 1 In Tables 1 to 6, as shown in Table 1, the aluminum alloy composition is within the scope of the embodiment of the present invention. In addition, the extruded material is manufactured under preferable manufacturing conditions such as performing hot isostatic pressing in an unrecrystallized region. Furthermore, solution treatment, quenching treatment, and artificial aging treatment are also performed under preferable production conditions.
As a result, Invention Example No. 1 to 6, as shown in Table 1, the normalized dispersion of the average particle diameter and particle size distribution of the fine particles is within the specified range of the embodiment of the present invention, the tensile strength is high strength of 800 MPa or more, and the total elongation is It has a high ductility characteristic of 5% or more.

On the other hand, Comparative Example No. 1 in Table 1 was used. In Tables 1 to 5, as shown in Table 1, the aluminum alloy composition is out of the range of the embodiment of the present invention. For this reason, these comparative example No. Nos. 1 to 5 show that extruded materials and simulated machine parts are manufactured by a preferable manufacturing method. However, as shown in Table 1, the normalized dispersion of the particle size distribution is out of the specified range, or the structure is within the specified range. However, the tensile strength is as low as less than 800 MPa, or the total elongation is low.
In Comparative Example 1, Zn deviates from the lower limit.
In Comparative Example 2, Mg deviates from the lower limit.
In Comparative Example 3, Mn deviates from the lower limit.
In Comparative Example 4, Mn deviates from the upper limit.
In Comparative Example 5, Zr deviates from the lower limit.

Further, in Comparative Examples 6 to 11 in Table 1, although the aluminum alloy composition is within the range of the embodiment of the present invention as shown in Table 1, the manufacturing conditions simulating the machine parts are out of the above range. As a result, in these comparative examples, the normalized dispersion of the average particle diameter and / or the particle size distribution of the fine particles can be pushed out of the specified range, the tensile strength can be as low as less than 800 MPa, and even the total elongation can be low.

Comparative Example 6 is an example where the homogenization temperature is too high. Therefore, the normalized dispersion of the average particle diameter and particle size distribution of the fine particles became excessive, and the tensile strength and the total elongation were reduced.

Comparative Example 7 is an example where the extrusion start temperature is too high. Therefore, the normalized dispersion of the particle size distribution increased and the tensile strength decreased.

Comparative Example 8 is an example in which the average cooling rate up to 50 ° C. after extrusion is too slow. Therefore, the average particle diameter of the fine particles became excessive, and the tensile strength was reduced.

Comparative Example 9 is an example in which the temperature of the artificial aging treatment is too high. Therefore, the normalized dispersion of the average particle diameter and particle size distribution of the fine particles became excessive, and the tensile strength was lowered.

Comparative Example 10 is an example in which the time for artificial aging treatment is too long. Therefore, the average particle diameter of the fine particles became excessive, and the tensile strength was reduced.

Comparative Example 11 is an example where the homogenization temperature is too low. Therefore, the normalized dispersion of the average particle diameter and particle size distribution of the fine particles became excessive, and the tensile strength and the total elongation were reduced.

This application is accompanied by a priority claim based on Japanese Patent Application No. 2016-161644, whose application date is August 22, 2016. Japanese Patent Application No. 2016-161644 is incorporated herein by reference.

According to an embodiment of the present invention, the mechanical part made of an extruded material of 7000 series aluminum alloy having a tensile strength after artificial aging treatment of 800 MPa or more and a total elongation of 5% or more is obtained, and its manufacture The method can provide a 7000 series aluminum alloy extruded material that is a material thereof. For this reason, embodiment of this invention can be used suitably as the said mechanical component reduced in weight.

Claims (6)

1. Zn: 8.0 to 14.0% by mass,
   Mg: 2.0 to 4.0% by mass,
   Cu: 0.5 to 2.0% by mass,
   Mn: 0.2 to 1.5% by mass,
   Zr: 0.05 to 0.3% by mass,
   The balance is made of aluminum and an aluminum alloy that is an inevitable impurity,
   The average particle diameter of fine particles in the crystal grains measured by X-ray small angle scattering is 2 nm or more and 7 nm or less,
   The normalized dispersion of the particle size distribution is 45% or less,
   A mechanical component having a tensile strength of 800 MPa or more and a total elongation of 5% or more.
2. Cr: 0.05 to 0.3% by mass,
   Sc: 0.05 to 0.3% by mass
   The machine part according to claim 1, further comprising one or two of them.
3. Ag: 0.05 to 0.5% by mass,
   Sn: 0.01 to 0.2% by mass
   The machine part of Claim 1 or 2 which further contains 1 type or 2 types of these.
4. Zn: 8.0 to 14.0% by mass,
   Mg: 2.0 to 4.0% by mass,
   Cu: 0.5 to 2.0% by mass,
   Mn: 0.2 to 1.5% by mass,
   Zr: 0.05 to 0.3% by mass,
   The balance is an extruded material for machine parts consisting of aluminum and an aluminum alloy which is an inevitable impurity,
   After simulating a machine part and making it a wire rod extruded material with a diameter of 25 mm having a circular cross section, a wire rod material having a reduction in area of 84% and drawing into a circular shape with a cross section of 10 mmφ was obtained. After a solution treatment for holding at a temperature of 480 ° C. for 5 hours, a quenching treatment was performed at an average cooling rate of up to 50 ° C. at 200 ° C./second, and then an artificial aging treatment was held at 120 ° C. for 72 hours. The average particle diameter of fine particles in the crystal grains measured by small-angle scattering is 2 nm or more and 7 nm or less, the normalized dispersion of the particle size distribution is 45% or less, the tensile strength is 800 MPa or more, and the total elongation is 5 % Extruded material characterized by being at least%.
5. Cr: 0.05 to 0.3% by mass,
   Sc: 0.05 to 0.3% by mass
   The extruded material according to claim 4, further comprising one or two of them.
6. Ag: 0.05 to 0.5% by mass,
   Sn: 0.01 to 0.2% by mass
   The extruded material according to claim 4 or 5, further comprising one or two of them.